Pure conjectural or anecdotal but it is my intuition that there is something to it
EDIT: My running theory is related to hormesis or tolerance where the body produces an opposite effect to the ligand to maintain homeostasis and there is not a sufficient dose of the exogenous drug taken to override the body’s compensatory reaction
So even tho caffeine is a stimulant (adenosine antagonist) it actually causes the body to produce the opposite reaction, causing the reverse effect of making you sleepy
IIRC it takes about 30ish minutes for caffeine to “kick in”. So if you have a bit, then take a nap, it can give you a nice 20ish minute power nap, then naturally wake you up so you don’t feel groggy. The key is to be able to fall asleep quickly enough to have a decent power nap before it kicks in.
Also, wild and vivid dreams.
This restonates ;)